Choosing Between a Relational Database and a NoSQL Database

This page presents information to help you decide whether to use a relational database, a NoSQL database, or a hybrid solution.


For an introduction to relational databases and NoSQL databases, see Types of databases.

Features of relational databases and NoSQL databases

The following table provides a high-level comparison of the characteristics of relational and NoSQL databases:

Relational databasesNoSQL databases
Moderate incoming data velocityHigh incoming data velocity
Data comes from one or a few locationsData comes from many locations
Primarily structured dataStructured and semi-unstructured data
Nested or complex transactionsSimple transactions
Protect uptime via failover or log shippingProtect uptime via architecture
High availabilityContinuous availability
Deploy an app to one serverDeploy an app to many servers
Primarily write data to one locationWrite data to any location
Primary concern is scaling readsScale writes and reads
Scale up for more users and dataScale out for more users and data
Maintain data volumes with purgesHigh data volumes retained forever

The following image visualizes the structures of various types of databases, as well as the data complexity that they accommodate by design:

The following table compares the characteristics of relational databases and NoSQL graph databases:

Relational databaseGraph database (NoSQL)
Simple-to-moderate data complexityHeavy data complexity
Hundreds of potential relationshipsBillions of potential relationships
Moderate JOIN operations and good performanceHeavy or extreme JOIN operations
Static to semi-static data changesDynamic, constantly changing data
Primarily structured dataStructured and unstructured data
Nested or complex transactionsSimple transactions
Always strongly consistentTunable consistency (eventual to strong)
Moderate incoming data velocityHigh incoming data velocity
High availabilityContinuous availability
Centralized applicationDistributed, location-independent application
Scale up for increased performanceScale out for increased performance

Questions to ask before choosing a NoSQL database

If you are evaluating whether a NoSQL database is appropriate for your production environment, you should address the following technical, business, and deployment considerations.

Technical Considerations

Before deciding to use a NoSQL database, ask the following technical questions:

  • Can the database serve as the primary data source for the online application?
  • Does the database have features that prevent the loss of critical data? Are writes durable in nature by default so that the data is safe?
  • Is the database fault-tolerant, and is it capable of providing continuous availability?
  • Can the database easily replicate data located in the same data center, across multiple data centers, and across different cloud availability zones?
  • Does the database offer read/write anywhere capabilities? (Can the system write to and read from any node in the cluster?)
  • Does the database provide a robust set of security features?
  • Does the database support backup and recovery procedures that are easy to create and manage?
  • Does the database require special caching layers?
  • Is the database capable of managing big data and delivering high performance regardless of data size?
  • Does the database offer linear scalability for adding new nodes?
  • Can new nodes be added and removed online without impacting your business?
  • Does the database support key platforms and developer languages?
  • Does the database provide a query language that is similar to SQL?
  • Can the database run on commodity hardware with no special requirements?
  • Is the database easy to implement and maintain for large deployments?
  • Does the database offer data compression that results in significant storage savings?
  • Is it easy to run analytic operations on the database?
  • Can the database easily interface with and support modern data warehouses or data lakes that use Hadoop?
  • Is it easy to carry out search operations and functions directly on the NoSQL database?
  • Can the database isolate the online, analytic, and search workloads within a single application?
  • Does the database have solid command-line and visual tools for development, administration, and performance management?

Business Considerations

The following list presents business-related questions that you should ask before deciding to use a NoSQL database:

  • Does a commercial entity back the database?
  • If so, does the commercial entity provide 24x7 enterprise-level support and
  • Does the database have professional online documentation?
  • Does the database have customers across a wide range of industries that use the product in critical production environments?
  • Does the database have an attractive pricing structure?
  • If the database is open source, does it have a thriving open-source community?

Deployment Considerations

You can use a NoSQL database as part of a new application, to augment an existing application, or to fully replace an application. Before choosing a database, consider your deployment needs.

New applications

Many organizations begin using NoSQL on a new application. This approach enables you to avoid rewriting applications, migrating data, and performing related tasks.


Some organizations choose to augment an existing system by adding a NoSQL component. This often happens with applications that have outgrown a relational database due to scale problems, the need for better availability, or other issues. Parts of the existing system continue to use the existing RDBMS, while the developers modify other application components to use the NoSQL database.

Rip and replace projects

If a system is too costly or is breaking due to increased user concurrency, data velocity, or data volume from cloud applications, you can replace it fully with a NoSQL database.

Guidelines for deciding between a relational database and a NoSQL database

The following questions can help you determine whether a relational database or a NoSQL database is best for your application.

  • Do you need a flexible data model that includes a combination of structured, semi-structured, and unstructured data?
  • Are complex JOIN operations overwhelming your RDBMS and slowing response times?
  • Do you care more about the value derived from the relationships between tables than the tables themselves?
  • Do you need continuous availability with redundancy in both data and function across one or more locations, rather than simple failover for the database?
  • Do you need a database that runs in multiple data centers and cloud availability zones?
  • Do you need to handle high-velocity data originating from sensors, mobile devices, and similar sources? If so, do you need to handle this data with extreme write speed and low-latency query speed?
  • Do you need to go beyond single-machine limits for scale-up? Does your system require a scale-out architecture that makes it easy to add more processing power and storage capacity?
  • Do you need to run different workloads (such as online, analytics, and search) on the same data without manually loading it onto separate systems or machines?
  • Do you need to manage a widely distributed system with minimal staff?

Get Support

For more information about relational databases and NoSQL databases, see the Managed Operations FAQ.

Learn more about Rackspace database services .

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